Physical and microchemical alterations of chrysotile and amosite asbestos in the hamster lung.

The physical and microchemical alterations of chrysotile and amosite asbestos (Union International Contre le Cancer standard samples) in the hamster lung and in vitro following acid treatments were studied by scanning electron microscopy (SEM) and x-ray energy-dispersive spectrometry (XEDS). Following intratracheal instillation, the ratio of short chrysotile fibers (less than 5 microns in length) decreased initially from 38% to 13% in the hamster lung, but increased again to 56% 2 years after the instillation. The majority of these new short chrysotile fibers had diameters less than 0.05 micron. Contrary to this, short amosite fibers (less than 5 microns in length) decreased from 41% initially to 4% 2 yr after instillating into the hamster lung. The diameters of amosite fibers appeared much less altered than that of chrysotile during the same time period. After 2 yr in the hamster lung, 33% of chrysotile and 68% of amosite found were asbestos bodies. The Si/Mg ratios of chrysotile fibers with diameters less than 0.2 micron were significantly higher than those with diameters between 0.2 and 0.6 micron in all groups: this relationship was reversed in all amosite groups. The Si/Mg ratios of the instillated and acid-treated chrysotile fibers were both higher than that of the same-sized control fibers. Acid treatments of chrysotile fibers in asbestos bodies from the hamster lung further altered their Si/Mg ratio. The Si/Mg ratios of the instillated amosite fibers were lower than that of the same-sized control fibers, but the difference between them disappeared following acid treatments. The hamster lung disposed of both chrysotile and amosite fibers smaller than 5 microns efficiently. Chrysotile and its asbestos bodies appeared to lose Mg ions and to fragment continuously in the hamster lung, and also in vitro with acid treatments. Amosite appeared also to fragment but lose more silicon than magnesium ions, at a much slower rate than that of chrysotile, presumably from the difference in their basic structures.